/*
    No.791 うし数列
    https://yukicoder.me/problems/no/791
*/
#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    string n;
    cin >> n;
    if (n[0] != '1') {
        cout << -1 << endl;
        return 0;
    }

    int cnt = count(n.cbegin(), n.cend(), '3');
    if (((int)n.size() - 1) == cnt) {
        cout << cnt << endl;
    } else {
        cout << -1 << endl;
    }
}